Detecting ciscuits



Jan. 2, 1923. 1,440,407

De LKFOSCBIO RR :5 rs

FILED JULY 2. I920.

rm F1 INVENTOR zwz i ATTORNEY 16 transmission Patented Jan. 2, 1923.

lJNlTED STATES,

HAROLD s. osnomm, or NEW Yoiix, N. Y.,

PATIENT, ore-ice,

sssmzion Tb ma lman rnnnrnonn AND TELEGRAPH comm, A conrona'non or new YORK.

nn'rnc'nne cmcoriis.

Application fled July 2;

ratus and more particularly to receiving apparatus to be used in connection with stems in which carrier currents are eriip oyed.

' Heretofore, when the carrier currents have been employed for the transmission of telegraphic signals either over wires or through the ether, it has been customary to translate the liigh frequency carrier currents into low frequency signals by means ofa detector, such as a vacuum tube detector, in

the-hutput circuit of which a. relay is ineluded. Since detectors of this type operate by controlling the flow of a direct current,

it has been necessary to use a neutral relay as the receiving instrument. One of the objects of the present invention is to provide polarized relay may be used for receiving purposes. Another object of the invention is to provide a detector circuit of such char acter that the receiving relay will be operatcd by the alternating current component of thesignaling current the direct current component being effectually suppressed. These objects, as well as other objects more fully appearing hereinafter, are obtained by means of the arrangement set forth in the following description, and illustrated in the appended drawings. Figure 1 of which constitutes a circuit diagram of a form of de tector circuit embodying the invention, and Figures 2 and 3 of which show curves illustratingthe operation of the detector.

Referring to Figure 1, D designates a detector of the vacuum tube type having a filament 1, plate 2 and controlling electrode or grid 3. The input circuit of the detector is connected between the filament 1 and the grid 3 and includes the secondary winding of a transformer 4'. through the agency of which received modulated carrier cur- 5U rcnts are impressed upon the detector. A source of potential 5 is included in the grid circuit for a purpose more fully appearing as wi 19cc. semi R0. 393,538.

' hereinafterL- The output circuitisconnect- S. Oseonnn;

ed between the-filament 1 and thmplate 2 and-includes a source-of space current B. The olarized receiving relay R having windlngs 6 and 7 is provided fol-recording the signals. The winding 6 of: the polarized relay'is bridged across the output circuit 'of-the detector in parallel with the winding 7. A condenser 8 shunted by a resistance 9 is included in series-with'thewinding 6, while an inductance 1) is included in series with; the winding 7; A condenser 11 is bridged across the output circuit to form a by-pass for currents of carrier frequency,

I appear later.

The operation is as follows:

Inductance 10 and resistance 9 are so proportioned that their resistances are equal, so that a direct current flowing in the output circuit "will divide equally between the windings 6 anti 7 of the olar relay. The armature of the relay is t erefore unbiased and will remain in whichever one ofits two positions it has been moved in response to 25 a detector circuit of such character that a.

a signal, until 'an impulse is impressed upon the relay of such polarity as to shift it to the other position. When signals are not being received the source 5 in the grid circuit is adjusted in a well-known manner, so that no current or substantially no current fiows'in the output circuit.

Asis well known, the modulation of a carrier frequency, in accordance with a signal wave of the character indicated bythe curve 12 of Figure 2, results in a composite wave which may be resolved into a number of components, including an unmodulatcd wave of carrier frequency, a wave having a frequency equal to the sum of the carrier frequency and the dot frequency of the signal pulse, and a were having a frequency corresponding to the difference between the carrier frequency and the dotv ireqnency. Since the signal pulse is not of sine wave form but tends to be square topped. it may be resolved into a sine wave of dot frequency, and a plurality of sine waves whose rcqucncies are harmonics of the dot frequency onsequently. in addition to the components above mentioned. the modulated carrier \\'u\'c comprises components equal to. the sums and difi'crcnccs between the carrier he quency and the harmonics of the dot frequency.

rVhen a composite wave of this character is impremed upon a vacuum tube detector such as the detector D, the component frequencies of the composite wave react upon each other in a manner similar to that already described in connection with the modulatmg process, so that waves appear in the output circuit of the detector, whose frequencies correspond to the sums and differences of the component frequencies. These different frequencies correspond to the dot frequency and the various harmonics'thereof, and combine with adirect current component caused by the change in the impedance of the. output circuit in response to the received signal to form a composite wave similar to that represented by the curve 12 of Figure 2, which of course corresponds to the signal originating at the transmitting station. The frequencies in the output circuit which correspond to the component frequencies of the modulated-wave and those frequencies corresponding to the sums of the component frequencies, are of no utility in recording the signal and should, therefore, be suppressed. For this purpose the condenser 11 is provided and is so adjusted as to form a path of low impedance to the high frequencies, so that these frequencies will be shunted from the receiving relay R. The composite wave indicated by the curve 12 of Figure 2 is impressed upon the receiving relay R as the condenser 11 offers a path of large impedance to the low frequencies corresponding to the dot or dash frequency and the harmonics thereof. Owing to the fact that the resistances of the path through the two windings 6 and 7 of the relay are equal, the direct current component of the signal pulse is without effect upon the polar relay. The reactances of the two paths are different, however, one being positive and one being negative. ('onsequcntly the alternatiug current components atfect the polar relay. The armature at this relay, when no signals are being received rests upon its right-hand contact, so that the local receiving circuit 13 is open. At the. beginning of the signaling pulse indicated by the curve 12 of Figure 2 the alternating current components produce a kick in the relay circuit, such as is indicated at 13 in Figure 3. this kick" corresponding to the change in amplitude as thesignal pulse indicated by the curve 12 rises from zero to its maximum value. The armature of the polar relay is therefore shifted to its left-hand contact and closes the local circuit 13. remaining in this posi lion during the steady state condition in which the direct. currcnt component, as alrczuly stair-d, is without cll'cct. Towards the cod of thc signaling pulsc. as wave 1:!

falls again to Zero. another kit-k" passes through the windings of the rela v ll in thc opposite direction as indicated at it in Figure 3, thereby shifting the armature of thc relay to its right-hand contact. During the steady state interval corresponding to no current, the armature remains in its shifted position until the beginning of a new signaling impulse when the operation is repeated.

It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated without departing from the s irit of the invention as defined in the followin claims:

lVhat is c aimed is:

1. A receiving circuit comprising a detector, a polar relay in the output circuit of said detector and controlled thereby and circuit connections between said detector and said polar relay including means for preventing the direct current component of a signaing pulse detected by said detector om a acting the lar relay.

2. A receiving circuit comprising a vac uum tube detector, a polar relay in the output circuit of said detector and controlled thereby and circuit connections including means for preventing thev direct current component of a. signaling pulse detected by said detector from affecting said polar relay.

3. A receiving circuit comprising a detec tor, a polar relay having two windings included in a parallel circuit with said de tector, the resistances of the parallel circuits through,the two windings being equal but the reactances being unequal, so that said polar relay is unafiected by the direct current component of a. signal pulse but is responsive to the alternating component thereof.

4. A receiving apparatus comprising a vacuum tube detector having a plurality of electrodes, and a )olar relay having two windings connected in parallel, the resist ances of the parallel circuits through said windings being equal but their rcactanccs being unequal, so that the polar relay is unresponsive to the direct current component of a signal pulse but is responsive to the alternating component thereof.

5. A receiving apparatus comprising a detector, at source of direct current for polarizing said dctcctor. and a polar receiving re lay having two windings connected in parallcl circuits with said detector and said source. the resistances of said parallel cir cuits being equal but the reactauccs being unequal, so that the polar relay is HHIQSPUII' sive to' direct current flowing from said source but is res )onsivc to thc alternating component of a signal pulsc.

(i. A. receiving apparatus comprising a. vacuum tube detector having filzuucut and plutc clcctroclcs, a sourcc of currcut councctcd hetwccu said clcctrodcs, and a receiving polar relay having two yvindings connected in parallel with ewch other, and in series with said source and said filament and plate electrodes, the resistances of the path through the two windings being equal but the reaetances unequal, so that said polar relay is unresponsive to direct current flowing from said source but is responsive to the alternating component of a signal pulse.

In testimony whereof I have signed my 10 name to this speciliration this 30th (lay of June 1920.

HAROLD S. OSBORNE. 

